German crowd favorites Tommy Haas and reigning champion Philipp Kohlschreiber secured berths in the final four, while top seed Janko Tipsarevic continued his recent struggles with a quarterfinal setback Friday at the BMW Open.
Germany's own Daniel Brands ousted the world No. 10 Tipsarevic 6-3, 4-6, 6-4 on the red clay at MTTC Iphitos.
Tipsarevic has had a slow start to his spring clay-court season with a loss in his first match at the Monte Carlo Masters, a quarterfinal setback last week in the Bucharest and Friday's ouster at the hands of Brands.
Meanwhile, the third-seeded 2000 Munich runner-up Haas handled sixth-seeded fellow German Florian Mayer 6-4, 6-1. Mayer was the Munich runner-up two years ago.
Two other quarterfinal affairs saw a fourth-seeded Kohlschreiber top Serb Viktor Troicki 6-3, 7-6 (7-3) and Croat Ivan Dodig upend fifth-seeded Ukrainian Alexandr Dolgopolov 6-4, 6-4.
Saturday's semifinals will pit the one-time world No. 2 Haas against Dodig and the two-time champion Kohlschreiber versus his 69th-ranked fellow countryman Brands. Kohlschreiber beat Croat Marin Cilic in last year's final and also titled here back in 2007.
This week's winner will claim $96,000.